The chemistry and the biological significance of the reactions between penicillins and specific bacterial proteins will be examined. Attempts will be made to define the role of bound penicillins in their bacteriocidal effects, their induction of penicillinase and their inhibition of bacterial sporulation. The penicillin binding characteristics and the enzymatic properties of purified penicillin binding proteins from penicillinase inducible bacteria, sporulating bacteria and vegetative, penicillin sensitive organisms will be compared. Efforts will be made to determine if penicillin resistant bacteria contain a separate, distinct penicillin binding component specific for the induction of penicillinase.